---
title: "CONNECT"
id: ecpg-sql-connect
pg_version: "20devel"
---

<a id="ecpg-sql-connect"></a>

# CONNECT — establish a database connection

## Synopsis

```
CONNECT TO connection_target [ AS connection_name ] [ USER connection_user ]
CONNECT TO DEFAULT
CONNECT connection_user
DATABASE connection_target
```

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## Description

The `CONNECT` command establishes a connection between the client and the PostgreSQL server. 

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## Parameters

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**`connection_target`**

 `connection_target` specifies the target server of the connection on one of several forms. <a id="ecpg-sql-connect-connection-target-database-name"></a>

**[ `database_name` ] [ `@``host` ] [ `:``port` ]**

 Connect over TCP/IP <a id="ecpg-sql-connect-connection-target-unix-domain-sockets"></a>

**`unix:postgresql://``host` [ `:``port` ] `/` [ `database_name` ] [ `?``connection_option` ]**

 Connect over Unix-domain sockets <a id="ecpg-sql-connect-connection-target-tcp-ip"></a>

**`tcp:postgresql://``host` [ `:``port` ] `/` [ `database_name` ] [ `?``connection_option` ]**

 Connect over TCP/IP <a id="ecpg-sql-connect-connection-target-constant"></a>

**SQL string constant**

 containing a value in one of the above forms <a id="ecpg-sql-connect-connection-target-host-variable"></a>

**host variable**

 host variable of type `char[]` or `VARCHAR[]` containing a value in one of the above forms  <a id="ecpg-sql-connect-connection-name"></a>

**`connection_name`**

 An optional identifier for the connection, so that it can be referred to in other commands. This can be an SQL identifier or a host variable. <a id="ecpg-sql-connect-connection-user"></a>

**`connection_user`**

 The user name for the database connection.  This parameter can also specify user name and password, using one the forms `user_name/password`, `user_name IDENTIFIED BY password`, or `user_name USING password`.  User name and password can be SQL identifiers, string constants, or host variables. <a id="ecpg-sql-connect-default"></a>

**`DEFAULT`**

 Use all default connection parameters, as defined by libpq. <a id="id-1.7.5.20.4.5"></a>

## Examples

Here a several variants for specifying connection parameters: 
EXEC SQL CONNECT TO "connectdb" AS main;
EXEC SQL CONNECT TO "connectdb" AS second;
EXEC SQL CONNECT TO "unix:postgresql://200.46.204.71/connectdb" AS main USER connectuser;
EXEC SQL CONNECT TO "unix:postgresql://localhost/connectdb" AS main USER connectuser;
EXEC SQL CONNECT TO 'connectdb' AS main;
EXEC SQL CONNECT TO 'unix:postgresql://localhost/connectdb' AS main USER :user;
EXEC SQL CONNECT TO :db AS :id;
EXEC SQL CONNECT TO :db USER connectuser USING :pw;
EXEC SQL CONNECT TO @localhost AS main USER connectdb;
EXEC SQL CONNECT TO REGRESSDB1 AS main;
EXEC SQL CONNECT TO AS main USER connectdb;
EXEC SQL CONNECT TO connectdb AS :id;
EXEC SQL CONNECT TO connectdb AS main USER connectuser/connectdb;
EXEC SQL CONNECT TO connectdb AS main;
EXEC SQL CONNECT TO connectdb@localhost AS main;
EXEC SQL CONNECT TO tcp:postgresql://localhost/ USER connectdb;
EXEC SQL CONNECT TO tcp:postgresql://localhost/connectdb USER connectuser IDENTIFIED BY connectpw;
EXEC SQL CONNECT TO tcp:postgresql://localhost:20/connectdb USER connectuser IDENTIFIED BY connectpw;
EXEC SQL CONNECT TO unix:postgresql://localhost/ AS main USER connectdb;
EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb AS main USER connectuser;
EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb USER connectuser IDENTIFIED BY "connectpw";
EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb USER connectuser USING "connectpw";
EXEC SQL CONNECT TO unix:postgresql://localhost/connectdb?connect_timeout=14 USER connectuser;
 

Here is an example program that illustrates the use of host variables to specify connection parameters: 
int
main(void)
{
EXEC SQL BEGIN DECLARE SECTION;
    char *dbname     = "testdb";    /* database name */
    char *user       = "testuser";  /* connection user name */
    char *connection = "tcp:postgresql://localhost:5432/testdb";
                                    /* connection string */
    char ver[256];                  /* buffer to store the version string */
EXEC SQL END DECLARE SECTION;

    ECPGdebug(1, stderr);

    EXEC SQL CONNECT TO :dbname USER :user;
    EXEC SQL SELECT pg_catalog.set_config('search_path', '', false); EXEC SQL COMMIT;
    EXEC SQL SELECT version() INTO :ver;
    EXEC SQL DISCONNECT;

    printf("version: %s\n", ver);

    EXEC SQL CONNECT TO :connection USER :user;
    EXEC SQL SELECT pg_catalog.set_config('search_path', '', false); EXEC SQL COMMIT;
    EXEC SQL SELECT version() INTO :ver;
    EXEC SQL DISCONNECT;

    printf("version: %s\n", ver);

    return 0;
}
 

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## Compatibility

`CONNECT` is specified in the SQL standard, but the format of the connection parameters is implementation-specific. 

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## See Also

[DISCONNECT](ecpg-sql-disconnect.md), [SET CONNECTION](ecpg-sql-set-connection.md)